A bogus caller, claiming to be from Yellow Pages, rings and checks business details for the next edition. But nothing more happens other than the firm is sent a large bill.

In the second scam, businesses are targeted by letter from abroad with what seems like a request to verify their details for inclusion in a European directory.

But the small print commits the business to pay #450 a year for an advert to be published and also that three months notice is needed to cancel the contract. Mick King, trading standards officer for Northumberland, said: "In these days of increasing workloads and fewer resources it is tempting to try to deal with what appears to be a simple request quickly, whether by phone or letter.

"However, spending just a little time on clarifying exactly what is being offered may save much time and expense in the future.

"It is rare for any service to be completely free these days so if in doubt, check it out."